1. Field of the Invention
This invention relates to the surface protective film suitable for adhesively protecting the surface of the plastic article containing the plasticizer, namely the surface of the polyvinyl chloride film or sheet containing the plasticizer coated on one side or the both sides of the metal plate or the ornamental veneer board until the secondary processing or the final finishing after manufacturing thereof.
2. Description of Prior Art
Heretobefore, a pressure sensitive adhesive film coated with an adhesive agent on a paper or the basic plastic film has been used as the surface protective film.
The said pressure sensitive adhesive film possesses the usual adhesive strength of the peeling velocity of 200 mm/min. under the condition of the loads of 20-200 grs., 180.degree.angle and 20mm width.
However, the said pressure sensitive adhesive film increases the strength of the adhesive layer and makes it difficult to peel off said film from the surface of the article namely the surface of the plastic sheet containing the plasticizer precoated on the metal plate or the ornamental veneer board and remains the adhesive layer (or agent) on the surface of the said article in a low temperature of less than 0.degree.C. While, the said film often lost the faculty of the protective film depressing the adhesive force to null value in a high temperature of more than 40.degree.C.
The said phenomenon is based on increasing the adhesive strength of the adhesive agent and on decreasing the fluidity of the plasticizer contained in the polyvinyl chloride film or sheet precoated on the metal plate or the ornamental veneer board in the low temperature, while the said phenomenon is based on increasing the fluidity of the plasticizer and oozing out the plasticizer at a boundary surface between the protective film or sheet and the surface of the article in the form of a film thereby depressing the adhesive force of the protective film.
In order to overcome the said disadvantages, it has been studied chemico-physical properties of the adhesive layer and found the adhesive composition having good quality.